export default function Base64() {
	// 私钥
	let _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
	// 加密
	this.encode = function (input) {
		var output = "";
		var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
		var i = 0;
		input = _utf8_encode(input);
		while (i < input.length) {
		chr1 = input.charCodeAt(i++);
		chr2 = input.charCodeAt(i++);
		chr3 = input.charCodeAt(i++);
		enc1 = chr1 >> 2;
		enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
		enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
		enc4 = chr3 & 63;
			if (isNaN(chr2)) {
				enc3 = enc4 = 64;
			} else if (isNaN(chr3)) {
				enc4 = 64;
			}
			output = output + _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
			 _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
			}
			return output;
        }
        // 解密
        this.decode =  (input)=> {
			var output = "";
			var chr1, chr2, chr3;
			var enc1, enc2, enc3, enc4;
			var i = 0;
			if (input==undefined||input==null){
			}else {
				input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
				while (i < input.length) {
 					enc1 = _keyStr.indexOf(input.charAt(i++));
					enc2 = _keyStr.indexOf(input.charAt(i++));
					enc3 = _keyStr.indexOf(input.charAt(i++));
					enc4 = _keyStr.indexOf(input.charAt(i++));
					chr1 = (enc1 << 2) | (enc2 >> 4);
					chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
					chr3 = ((enc3 & 3) << 6) | enc4;
					output = output + String.fromCharCode(chr1);
					if (enc3 != 64) {
						output = output + String.fromCharCode(chr2);
					}
					if (enc4 != 64) {
						output = output + String.fromCharCode(chr3);
					}
				}
				output = _utf8_decode(output);
				return output;
            }
 
        }
        // private method for UTF-8 encoding
        let _utf8_encode =  (string)=> {
			string = string.replace(/\r\n/g,"\n");
            var utftext = "";
            for (var n = 0; n < string.length; n++) {
            	var c = string.charCodeAt(n);
                if (c < 128) {
                	utftext += String.fromCharCode(c);
                } else if((c > 127) && (c < 2048)) {
                    utftext += String.fromCharCode((c >> 6) | 192);
                    utftext += String.fromCharCode((c & 63) | 128);
                } else {
                    utftext += String.fromCharCode((c >> 12) | 224);
                    utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                    utftext += String.fromCharCode((c & 63) | 128);
                }
       	 	}
        	return utftext;
        }
        // private method for UTF-8 decoding
        let _utf8_decode = (utftext)=> {
       		var string = "";
            var i = 0;
            var c = c1 = c2 = 0;
            var c1 = 0;
            var c2 = 0;
            var c3 = 0;
            while ( i < utftext.length ) {
            	c = utftext.charCodeAt(i);
               		if (c < 128) {
                    string += String.fromCharCode(c);
                   		i++;
                    } else if((c > 191) && (c < 224)) {
                        c2 = utftext.charCodeAt(i+1);
                       	string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
                        i += 2;
                    } else {
                       	c2 = utftext.charCodeAt(i+1);
                        c3 = utftext.charCodeAt(i+2);
                        string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
                        i += 3;
                   }
                }
            return string;
        }
}
